Helicobacter pylori and gastric cancer

The concept of immune surveillance against tumors. The first theories

The immune system plays a major role in the surveillance against tumors. To avoid attack from the immune system, tumor cells develop different strategies to escape immune surveillance. Evidence of immune surveillance comes from both animal models and clinical observations. Mice with a wide variety of immunodeficiencies have a high rate of tumor incidence and are more susceptible to transplanted or chemical carcinogen-induced tumors. Immunosuppressed patients have a high incidence of tumors. However, many patients develop cancer even in the presence of an apparently normal immune system. This indicates that tumor cells are able to escape immune surveillance. The aim of this review article is to summarize the literature concerning the development of the theory of immune surveillance against tumors; to discuss the evidence for and against this theory, and to discuss the concept of immunoediting. Finally, the current approaches in anti-tumor immunotherapy will be analyzed.

Determinação histopatológica da presença do helicobacter pylori em câncer gástrico

RACIONAL: A causa do câncer gástrico (CG) é controversa e tem vários fatores envolvidos no seu processo de carcinogênese, incluindo o Helicobacter pylori (Hp) O papel da infecção pelo Hp no CG permanece incerto, com vários estudos controversos. OBJETIVO: Correlacionar a presença da infecção pelo Hp com câncer gástrico, através de exame anatomopatológico convencional do estômago ressecado. MÉTODO: Noventa e um pacientes tratados por ressecção cirúrgica foram revistos. O exame anatomopatológico foi feito em todos os pacientes para determinar a presença de infecção por Hp, metaplasia intestinal (MI) e confirmação do tipo histológico por hematoxilina-eosina. A análise estatística foi realizada através do qui-quadrado e testes de log-rank. RESULTADOS: MI foi observada em 81 tumores (89%). Em geral, a presença de infecção pelo Hp foi observada em 46 casos (50,5%). Não houve associação entre idade e Hp. Nos grupos de pacientes com CG avançado e precoce, a infecção pelo Hp estava presente em 47,7% e 54% dos tumores. A infecção pelo Hp ocorreu em 40 tumores (49%) no grupo de pacientes com MI. Nos com tumores sem MI, Hp estava presente em cinco (50%). Tumores proximais tiveram mais infecção por Hp, quando comparados aos tumores distais. CONCLUSÕES: A taxa de infecção não teve associação significativa com o tipo histológico, sexo, MI ou estágio de desenvolvimento tumoral. Esses resultados podem indicar que a participação da infecção pelo Hp durante o desenvolvimento do CG não pode ser descartada; no entanto, provavelmente não é essencial em todas as fases e o mecanismo do CG pode ser distinto da gastrite crônica e MI. Finalmente, é possível que a associação proposta é mera coincidência e que não há nenhuma influência real das bactérias no processo de carcinogênese.

Possible association of Helicobacter pylori infection with laryngeal cancer risk: an evidence-based meta-analysis

BACKGROUND

Infection with Helicobacter pylori (H. pylori) is a major cause of various gastric diseases and has been reported to play a role in the process of tumorigenesis and progression of gastric carcinoma. However, whether H. pylori infection increases susceptibilities to other cancers is not fully understood. Several studies have been devoted to the relationship between H. pylori infection and laryngeal cancer risk and have yielded conflicting results. In this study, we aimed to evaluate the possible association of H. pylori infection with laryngeal cancer risk.

METHODS

The associated literature was acquired through deliberate searching and selected based on the established inclusion criteria for publications. Extracted data were further analyzed by a systematic meta-analysis.

RESULTS

A total of 15 papers were identified. Of these, five case-control studies were selected. Laryngeal cancer risk for H. pylori infection was 2.03-fold (95% CI=1.28-3.23) (Z=3.00, p<0.01) compared with the controls.

CONCLUSIONS

The pooled data suggest infection with H. pylori as a possible risk factor for laryngeal cancer.

Does the immune system see tumors as foreign or self?

Given the vast number of genetic and epigenetic changes associated with carcinogenesis, it is clear that tumors express many neoantigens. A central question in cancer immunology is whether recognition of tumor antigens by the immune system leads to activation (i.e., surveillance) or tolerance. Paradoxically, while strong evidence exists that specific immune surveillance systems operate at early stages of tumorigenesis, established tumors primarily induce immune tolerance. A unifying hypothesis posits that the fundamental processes of cancer progression, namely tissue invasion and metastasis, are inherently proinflammatory and thus activating for innate and adaptive antitumor immunity. To elude immune surveillance, tumors must develop mechanisms that block the elaboration and sensing of proinflammatory danger signals, thereby shifting the balance from activation to tolerance induction. Elucidation of these mechanisms provides new strategies for cancer immunotherapy.

Helicobacter pylori infection in children and adults: a single pathogen but a different pathology

BACKGROUND

The aims of this retrospective study were to ascertain in large series of children and adults: the relationship of the infecting strain to gastric mucosal lesions; and the relationship of the infecting strain to its duodenal localization.

MATERIALS AND METHODS

We studied 307 and 604 consecutive children and adults. In gastric mucosal samples H. pylori was cultured, genotyped and histologically assessed, while inflammation, activity and intestinal metaplasia were graded. In a subset of 171 patients H. pylori ureaseA (ureA) and cagA genes were amplified (PCR) using mucosal biopsies from the duodenum.

RESULTS

H. pylori infection was diagnosed in 40 children and 308 adults. cagA was identified in 50% and 65.5% of infected children and adults. Antral activity was associated with the density of infecting bacteria (p <.001) and with cagA (p <.01). Intestinal metaplasia was correlated with cagA (p <.001). The ureA gene was found in 56 duodenal samples from 82 H. pylori positive patients. Duodenal H. pylori ureA was significantly more frequent in patients with duodenal diseases than in those without (p <.01), cagA positive strains being mainly involved in the infection of this anatomical area (p <.01).

CONCLUSIONS

A severe H. pylori-associated gastritis is more prevalent when the density of infecting bacteria is high and when cagA positive strains cause the infection. The most virulent cagA positive H. pylori colonizes not only the gastric, but also the duodenal mucosa, which can be directly damaged by the bacteria itself or by its products.

Helicobacter pylori does not mediate the formation of carcinogenic N-nitrosamines

BACKGROUND

Both N-nitroso compounds and colonization with Helicobacter pylori represent known risk-factors for the development of gastric cancer. Endogenous formation of N-nitroso compounds is thought to occur predominantly in acidic environments such as the stomach. At neutral pH, bacteria can catalyze the formation of N-nitroso compounds. Based on experiments with a noncarcinogenic N-nitroso compound as end product, and using only a single H. pylori strain, it was recently reported that H. pylori only displays a low nitrosation capacity. As H. pylori is a highly diverse bacterial species, it is reasonable to question the generality of this finding. In this study, several genetically distinct H. pylori strains are tested for their capacity to form carcinogenic N-nitrosamines.

MATERIALS AND METHODS

Bacteria were grown in the presence of 0-1000 microM morpholine and nitrite (in a 1 : 1 molar ratio), at pH 7, 5 and 3.

RESULTS

Incubation of Neisseria cinerea (positive control) with 500 microM morpholine and 500 microM nitrite, resulted in a significant increase in formation of N-nitrosomorpholine, but there was no significant induction of N-nitrosomorpholine formation by any of the H. pylori strains, at any of the three pH conditions.

CONCLUSION

H. pylori does not induce formation of the carcinogenic N-nitrosomorpholine in vitro. The previously reported weak nitrosation capacity of H. pylori is not sufficient to nitrosate the more difficulty nitrosatable morpholine. This probably also holds true for other secondary amines. These results imply that the increased incidence of gastric cancer formation that is associated with gastric colonization by H. pylori is unlikely to result from the direct induced formation of carcinogenic nitrosamines by H. pylori. However, this has to be further confirmed in in vivo studies.

Recurrence and survival after resection of adenocarcinoma of the gastric cardia. Rotterdam Esophageal Tumor Study Group

In a retrospective study, the results after resection of carcinoma of the gastric cardia in the era without neoadjuvant therapy or extended lymph node dissection were evaluated. All 184 patients who underwent resection between January 1983 and December 1993 were included. Recurrence of disease, survival and prognostic factors were determined. The overall cumulative 5-year recurrence rate was 71% and the survival rate 23%. Multivariate analysis identified locoregional lymph node and distant metastases as the crucial prognosticators of recurrence of disease and survival. These results were similar to those from a previous study concerning our patients operated during the years 1983-88. The prognosis of a resected cardiacarcinoma has remained unchanged in our hands over the past 10 years. These results stress the importance of exploring new ways, such as the use of new diagnostic tools, to optimize preoperative patient selection and more aggressive treatment regimens to improve final outcome.

Timing of N-methyl-N-nitrosourea administration affects gastric carcinogenesis in Mongolian gerbils infected with Helicobacter pylori

In Mongolian gerbils, the gastric mucosa shows dramatic changes after Helicobacter pylori inoculation. The influence of the timing of N-methyl-N-nitrosourea (MNU) administration after H. pylori inoculation on gastric carcinogenesis was investigated. Ninety-two gerbils were divided into four groups. One group was given MNU at 24 weeks, and another at 1 week, after H. pylori inoculation. The other groups received only MNU. Stomachs were excised for histological examination 20 weeks after completing the MNU treatment. Carcinomas arose only in animals given MNU 1 week after H. pylori inoculation. In the relationship between H. pylori and gastric carcinogenesis, H. pylori is a promoter rather than an initiator, and other environmental factors (the timing of MNU administration) play important roles.

Polymorphonuclear oxidative burst after Helicobacter pylori water extract stimulation is not influenced by the cytotoxic genotype but indicates infection and gastritis grade

H. pylori-associated gastric mucosal inflammation is characterized by the presence of polymorphonuclear (PMN) leukocyte infiltrate, which is more severe when the infecting strain is cagA positive. After appropriate stimuli, such as bacterial products, PMN release large amounts of oxygen derived free radicals and proteases, to kill the bacterium. H. pylori seems to be particularly resistant to the oxidative machinery of PMN, which can in turn damage the host gastric mucosa. We evaluated peripheral PMN oxidative burst response after stimulation with water extracts from cagA positive (WEcagA+) or negative (WEcagA-) H. pylori strains in infected (n=31) and non-infected patients (n=32) in comparison with healthy controls (n=16); the influence of gastric mucosal inflammatory infiltrate and activity grade on PMN oxidative burst were also assessed. PMN oxidative burst was measured by FACS analysis. H. pylori water extracts were obtained from bacterial culture. H. pylori genotype was determined by means of the polymerase chain reaction. The PMN oxidative burst in H. pylori infected patients was significantly higher than that in H. pylori negative or healthy controls, no differences being found when the results following WEcagA+ and WEcagA- stimulation were compared. The difference in PMN oxidative burst obtained after WEcagA- and E. coli (standard stimulus for PMN oxidative burst) stimulation discriminated H. pylori infected from non-infected patients with a sensitivity of 90% and a specificity of 97%. The grade of PMN oxidative burst correlated with PMN infiltration grade of the gastric mucosa. Our findings allow to conclude that PMN oxidative burst activation by H. pyloriWE is species- but not strain-correlated. PMN priming, probably consequent to the action of soluble mediators released by mononuclear cells, makes PMN hyper-responsive to H. pylori products, thus favoring the release in the gastric mucosa of infected patients of large amounts of oxygen-derived free radicals, which are not enough to eliminate the infection, but may contribute to damaging the gastric mucosa itself. Peripheral PMN oxidative burst response to H. pyloriWE might furthermore be of help in diagnosing H. pylori infection.

Helicobacter pylori non-cytotoxic genotype enhances mucosal gastrin and mast cell tryptase

AIMS

To determine the association, if any, between H pylori genotype and the gastric mucosal variations in the levels of gastrin, somatostatin, tryptase, and histamine.

METHODS

49 patients affected by duodenal ulcer and 48 by non-ulcer dyspepsia were studied. To identify the H pylori genotype, the presence of the cagA gene and vacA alleles m1, m2, s1, and s2 were analysed by polymerase chain reaction. Gastrin, somatostatin, tryptase, and histamine were measured in antral mucosal biopsies.

RESULTS

57 patients were infected with H pylori (30 with duodenal ulcer and 27 with non-ulcer dyspepsia). Gastrin and tryptase were increased in patients with H pylori infection, although the variations were statistically significant only for gastrin; somatostatin and histamine were not influenced by H pylori infection. In patients with non-ulcer dyspepsia the absence of the cagA gene and the presence of vacA alleles s2 and m2 were associated with higher values of tryptase and to a lesser extent of gastrin. These associations were not found in patients with duodenal ulcer.

CONCLUSIONS

The cagA negative s2m2 strain of H pylori may be less dangerous for the gastric mucosa than other H pylori strains since it enhances tryptase production by gastric mucosal mast cells; this enzyme is thought to stimulate tissue turnover and favour wound healing.

Is infection control an academic study?

This editorial aims to answer the question of whether infection control is an academic specialty. By considering the consequences of a lack of infection control in terms of patient morbidity and mortality and hence cost, it is easy to establish the importance of the area. Infection control embraces not only developing policies for preventing the physical spread of a micro-organism but also prophylactic therapy such as vaccination and therapeutic measures such as antibiotics. Infection control not only applies to localized infection in hospital due to antibiotic resistant microbes but also to the community. Bacteria such as Helicobacter pylori and Chlamydia pneumoniae and the viruses hepatitis B, hepatitis C, human lymphotropic virus type 1, Epstein-Barr viruses and human papilloma virus have been implicated in diseases not previously thought to have an infectious origin. Coping with these problems is clearly an academic area.